This object, known as Nemesis, was hypothesized to pass through a portion of the Oort cloud approximately every 26 million years, bombarding the inner Solar System with comets. Halley-family comets, named for their prototype, Halley's Comet, are unusual in that although they are short-period comets, it is hypothesized that their ultimate origin lies in the Oort cloud, not in the scattered disc. [60] It would monitor distant stars with a photometer, looking for transits up to 10,000 au away. NASA's WISE spacecraft, scanning the entire sky at infrared wavelengths, has delivered new insights about these distant wanderers. It is also referred to as the Opik-Oort Cloud. It is thought that the Oort Cloud may extend 1/3 of the distance between our sun and the next star, which is around 1,000 and 100,000 AU (astronomical units). [4] The inner Oort cloud is also known as the Hills cloud, named after Jack G. Hills, who proposed its existence in 1981. [60] The observatory was proposed for halo orbiting around L2 with a suggested 5-year mission. Theoretical cloud of planetesimals at the far edge of the solar system, This article is about the outer Oort cloud. Yet somehow it will be another 10 to 28, before that same sunlight reaches the inner edge of the Oort Cloud, and perhaps as much as a. before the sunlight passes beyond the Oort Cloud’s outer edge. The Oort Cloud is the most distant region in our solar system, and it's jaw-droppingly far away,extending perhaps one-quarter to halfway from our Sun to the next star. [4], Models by Julio Ángel Fernández suggest that the scattered disc, which is the main source for periodic comets in the Solar System, might also be the primary source for Oort cloud objects. [46] This process could also scatter Oort cloud objects out of the ecliptic plane, potentially also explaining its spherical distribution. The outer Oort cloud may have trillions of objects larger than 1 km (0.62 mi),[4] and billions with absolute magnitudes[17] brighter than 11 (corresponding to approximately 20-kilometre (12 mi) diameter), with neighboring objects tens of millions of kilometres apart. The other four probes currently escaping the Solar System either are already or are predicted to be non-functional when they reach the Oort cloud; however, it may be possible to find an object from the cloud that has been knocked into the inner Solar System. [4][19] Oort: The structure of the cloud of comets surrounding the Solar System and a hypothesis concerning its origin. Some planetesimals were ejected from the solar system entirely, while others were flung into eccentric orbits where they were still held by the Sun’s gravity, but were far enough out that galactic influences also tugged on them. They could not survive at temperatures and pressures found on or around Earth.
The outer cloud is only weakly bound to the Sun and supplies the long-period (and possibly Halley-type) comets to inside the orbit of Neptune. According to these models, the number of collisions early in the Solar System's history was so great that most comets were destroyed before they reached the Oort cloud. It's called the Oort Cloud. In the 1980s, there was a concept for a probe that could reach 1,000 AU in 50 years, called TAU; among its missions would be to look for the Oort cloud.
But what’s the difference between them?